RU2540966C1 - Static converter - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention is related to the sphere of electric engineering and may be used in static converters for provision of uninterrupted power supply to consumers of three-phase alternating current. The static converter comprises input terminals for connection to the main alternating-current source and terminals for connection to the backup direct-current source, contactors, phase chokes, rectifier, filtering capacitor, and inverter. Being a power supply source with double energy conversion the static converter provides transfer from networking to autonomous operation without interruption of its function when required. To this end in order to connect direct-current source positive and negative terminals are connected through the contactor to the main rectifier operating in standard mode from the alternating-current network. Positive terminal is connected through diodes with chokes in the circuit of each alternating-current phase at the rectifier input while negative terminal is connected to the common negative point of this rectifier. The rectifier is based on transistor choppers ensuring voltage regulation at supply by the direct-current source. Voltage from the rectifier is filtered by a capacitor and comes to input of the inverter converting direct current to three-phase alternating current supplied to the load. A group of galvanic isolation is connected directly to the direct-current source and at the output - to output terminals of the main rectifier.

EFFECT: reduction of installed capacity, weight and dimensions.

1 dwg

Description

Technical field

The invention relates to static converters for supplying critical consumers of three-phase alternating current, the malfunction of which can lead to situations that pose a danger to human life, equipment damage, vehicle failure, etc.

This type of static converter must be supplied with electricity from at least two independent sources. As a backup source of power supply for responsible AC consumers, the most widely used are rechargeable batteries (AB). For example, the energy systems of modern nuclear submarines (NPS) incorporate several autonomous AC turbine generators using steam from the reactor, and a battery as a backup source of energy for idle turbine generators, as well as machine and static electric current converters for charging batteries. The main power submarine networks are three-phase alternating current with voltage of 380 V 50 Hz and direct current with voltage of 175-320 V (A.B. Karakaev, B. S. Markitanov “Electric networks of submarines.” State Maritime Academy named after S.O. Makarov , St. Petersburg, 2003).

The most complete options for circuit solutions of power nodes of modern three-phase static converters of medium and high power, operating according to the uninterruptible power supply circuit, are presented in the article by Klimov V.P., Moskalev A.D. Three-phase "UPS: circuitry and technical specifications." Electronic Components, No.6, 2005

According to this review, uninterruptible power supplies (UPS) with double energy conversion are the most common, providing a transition from mains mode to autonomous without interruption of power supply, providing the necessary shape and symmetry of a three-phase output voltage.

There are three groups of double energy conversion UPS circuits.

According to the first group, the classical structure of a UPS with an AB in the inverter power supply circuit includes a series-connected bridge controlled thyristor rectifier, a three-phase bridge voltage inverter using IGBT transistors, a three-phase output transformer with windings connected according to a delta-star circuit, and an output filter. A high-voltage battery is connected to the output of a controlled rectifier. These UPSs have high reliability indicators, however, they are characterized by increased weight and size indicators.

The second group consists of a UPS with a booster in the power circuit of the inverter. Their distinctive feature is the lack of a transformer, the use of an uncontrolled rectifier and the presence of a booster - power factor corrector in the power circuit. The rechargeable battery, as a rule, consists of two sections with a midpoint connected to a neutral wire. This group of converters also has disadvantages associated with significant weight and size characteristics and certain limitations of the power range.

The desire to increase the power factor in a wide range of load changes and improve the dynamic characteristics of the UPS on the one hand and the appearance of high-voltage high-speed power IGBT modules available for widespread use led to the appearance of a UPS structure with a bi-directional pulse-width (PWM) bridge converter.

The structure of such a UPS contains serially connected: an input three-phase PWM converter on IGBT transistors, phase chokes and storage capacitors, a voltage converter, a three-phase bridge inverter and an output filter. The circuit also contains a voltage converter, connected to the output of the input PWM converter by an input, and an output to the battery. The voltage converter works as a charger in a network mode of operation and as a battery booster in an autonomous mode.

The disadvantages of this circuit include a large number of power IGBT transistors in the power circuit and the occurrence of significant switching voltages on closed transistors, as well as a complex PWM transistor control circuit that requires information not only about the magnitude of currents and voltages, but also about their phase shift , which as a whole leads to sufficiently large weight and size characteristics and insufficient reliability.

Closest to the proposed invention in essence is the static AC converter adopted for the prototype, powered from the main three-phase alternating current network and the backup DC network, according to the RF patent No. 2481691.

The static converter, which is a power source with double energy conversion, provides, if necessary, the transition from the main mode to the standby mode with a minimum power outage due to the use of the following connection scheme. The positive terminal of the DC source through the contactor is connected to the rectifier, operating in the main mode from the AC network, through diodes with inductors in each phase of the alternating current, and the negative terminal of the DC source is connected to the common point of this rectifier. The rectifier is made on the basis of transistor choppers, providing voltage regulation when powered by a DC source. Almost all the blocks of the circuit involved in the main power supply are also used for backup power, which greatly simplifies the circuit. As a result, the mass and dimensions of the converter are reduced, which leads to increased reliability.

In addition, the plus and minus terminals of the DC source can be connected to the output of the main rectifier, which operates in the normal mode from the AC mains, through a group of high-frequency inverters, transformers, and a second additional rectifier connected in series. This increases reliability by introducing galvanic isolation of the two supply networks. However, such a switching circuit requires a significant increase in the installed power of the galvanic isolation group, comparable to the power transmitted through the main power supply by alternating current, and therefore the overall dimensions of the entire converter will be quite large.

Disclosure of invention

The aim of the invention is to provide uninterrupted power to consumers with a short-term loss or decrease in the input AC voltage while significantly reducing the installed power and overall dimensions of the galvanic isolation group and the entire converter.

The essence of the invention lies in the fact that the galvanic isolation group is directly connected at the input to the DC terminals, and its output is to the output of the main rectifier of the AC circuit. In this case, the operation time of the galvanic isolation group is determined only by the switching time of the power contactors of the supply circuits. This allows you to reduce the significantly weight and size characteristics of the galvanic isolation group and, therefore, the entire Converter.

According to the invention, a static converter for supplying critical consumers of three-phase alternating current includes input three-phase alternating current terminals and input direct current (positive and negative) terminals, as well as contactors, a main rectifier connected via input (through phase chokes and one of the contactors) to three-phase AC input terminals, a filter capacitor and an inverter connected in parallel with the rectifier output, while the positive input DC terminal current through another contactor and isolation diodes is connected to the connection points of each phase choke with the first contactor, and the negative DC terminal through the second contactor is connected to the common minus point of the rectifier containing transistor choppers, providing voltage regulation, the circuit connecting the DC terminals and a rectifier includes a galvanic isolation group consisting of a high-frequency inverter, a transformer and an additional rectifier.

The galvanic isolation group at the input is connected directly to the DC source, and at the output it is connected to the output terminals of the main rectifier.

Thus, the outputs of the main rectifier and, in addition, the galvanic isolation rectifier are connected in parallel. Therefore, when the input AC voltage disappears for a short time, AC consumers are instantly supplied with power through the galvanic isolation group, since time is not required to connect it. In the meantime, through the control system, a constant voltage is connected through dividing diodes and contactors to the input of the main rectifier, which takes from fractions to several seconds, during which the supply of responsible consumers goes through a galvanic isolation group. Since the operating time of the galvanic isolation group is determined only by the time the main rectifier is connected to the DC circuit, the overall dimensions of the galvanic isolation elements can be significantly reduced due to the short time of its operation and, accordingly, low heating of its constituent elements.

Thus, the proposed technical solution provides uninterrupted power supply to consumers during a short-term loss or decrease in the input AC voltage and improves the overall dimensions of the galvanic isolation group and the entire static AC converter of the converter as a whole.

Graphic illustration

The drawing shows an electrical diagram of a static converter.

The implementation of the invention

The static converter contains input terminals 1 for supplying a three-phase alternating current, a triple contactor 2 for switching on / off an alternating current circuit, input terminals 3 for supplying a direct current, a double contactor 4 for switching on / off a direct current circuit, and also chokes 5 in a circuit of each phase, rectifier 6, filtering capacitor 7, inverter 8. The positive input terminal of the direct current supply is connected through a contactor 4 to the three phase inputs of the rectifier b through dividing diodes 9, negative glue ma is connected through a contactor 4 to a common point of the rectifier 6. The rectifier 6 is provided on the base of transistor choppers providing voltage regulation when powered by DC supply. At the same time, three of its arms incorporate IGBT transistors 10 shunted by diodes 11. Three other arms are made on power diodes 12.

The DC input terminals 3 are also connected to a group of series-connected: a high-frequency inverter 13, a transformer 14, and an additional unregulated rectifier 15. The outputs of the additional rectifier 15 are connected to the outputs of the main rectifier 6, respectively, plus and minus, minus and minus.

A static converter designed to power critical AC consumers works as follows.

When AC voltage is supplied from the main power source to terminals 1, contactor 2 is turned on, and three-phase AC voltage is supplied through the chokes 5 to the main adjustable rectifier 6. Next, the rectified voltage is filtered by a capacitor 7 and fed to the input of the inverter 8, which generates alternating current at the output, which goes to the load.

The galvanic isolation group is constantly connected to the output of the main rectifier 6. Namely, the DC voltage from the terminals 3 passes through the closed contacts of the contactor 4 to the high-frequency inverter 13, after which the alternating voltage is brought to the desired value by the transformer 14 and turns into a constant additional rectifier 15. If it disappears alternating voltage through the galvanic isolation group for several seconds provides AC power to responsible consumers without power jerks.

At the same time, at the moment of loss of alternating voltage at the input terminals 1, the contactor 2 is turned off, the contactor 4 is turned on and the constant voltage available on the terminals 3 is supplied from the positive terminal through the contactor 4 to the diode diodes 9 and then to the chokes 5, then to the input of the rectifier 6. A the negative terminal through the contactor 4 is connected to the common negative point of the rectifier 6. In this case, the rectifier 6 generates a unipolar ripple voltage, which is then smoothed by the capacitor 7, is inverted on the inverter 8 and already this received alternating voltage goes to the load. And in this way, the transition from power through the galvanic isolation group to power through separation diodes 9 and the main rectifier 6 is carried out.

Since the galvanic isolation group is connected to the terminals 3 of the direct current source directly without turning on / off the keys, its voltage instantly appears at the output of the rectifier 6, while the voltage passed through the diodes 9 at the input of the rectifier 6 is delayed due to the presence of on / off switches and an external control circuit that switches two networks and regulates the voltage at the output of the static converter

As elements of a static converter can be used:

rectifier 6 - rectifier on choppers (IGBT-transistors and diodes), made according to the bridge circuit;

filter capacitor 7 - electrolytic capacitor;

inverter 8 - inverter according to a three-phase bridge circuit;

separation diodes 9 - power diodes of the semiconductor type;

high-frequency inverter 13 - inverter according to a single-phase bridge circuit;

additional rectifier 15 - diode rectifier according to a single-phase bridge circuit.

Based on the invention, a prototype of a static AC converter was manufactured and successfully tested.

Claims (1)

A static converter for powering critical consumers of three-phase alternating current, including the input three-phase alternating current terminals and the input direct current terminals (positive and negative), as well as contactors, the main rectifier connected through the input (through phase chokes and one of the contactors) to the terminals input three-phase alternating current, a filtering capacitor and an inverter connected in parallel with the output of the rectifier, while the positive terminal of the input DC through another the contactor and isolation diodes are connected to the connection points of each phase reactor with the first contactor, and the negative DC terminal is connected through the second contactor to the common minus point of the rectifier containing transistor choppers that provide voltage regulation, and the circuit connecting the DC terminals and the rectifier includes also a galvanic isolation group consisting of a high-frequency inverter, a transformer and an additional rectifier, characterized in that the group g the isolation is connected directly to the DC source, and the output to the output terminals of the main rectifier and turns on only for a short time, determined by the switching time of the power contactors of the supply circuits.